The present invention relates to solenoid operated valves of the type having a supply or inlet port and a pressure control outlet port and an exhaust port through which fluid is discharged to a sump or pressure source return. Such valves are employed to provide electrical control of a fluid pressure signal by controlling the flow of fluid from the inlet port to a valving chamber communicating with the pressure control port and also controlling the amount of fluid bleed to the exhaust for maintaining the desired pressure at the pressure signal outlet port.
Solenoid valves of the aforesaid type have found widespread usage in controlling the flow of hydraulic fluid in automatic transmissions for motor vehicles. In such transmissions the shifting of the transmission speed ratios is controlled by an electronic controller providing an electrical signal to the solenoid operated valve which provides a fluid pressure signal to a pressure responsive actuator for effecting the transmission speed ratio change.
Known valves employed in automatic transmission shift control have utilized a ball valve member disposed in the valving chamber with the ball moved with respect to a valve seat by an operating rod connected to the solenoid armature for controlling flow from the supply port to the valving chamber. However, valves of this type have encountered instability and flutter of the ball valve member upon exposure to hydraulic transients in the system and vibration encountered by the transmission. Efforts to counteract such instability and valve flutter in solenoid operation transmission shift control valves have utilized stiffer bias springs acting against the ball valve. This results in greater force and increased power requirements for the solenoid. For applications requiring a plurality of shift control valves a prohibitively high power consumption for the valves is the result.
The aforesaid solenoid valves employing a ball valve member have been found particularly susceptible to flutter when the ball valve member is in a position to substantially restrict the flow or near the closed position where the flow velocity is increased over the valve seat. It therefore has long been desired to provide a simple and relatively low cost way or means of reducing or eliminating the flutter in a solenoid operated pressure control valve and particularly valves of the type employing solenoid operating off of low voltage power supply widely employed in motor vehicle applications.
The present invention provides a solenoid operated pressure control valve having a supply inlet port valved by a raised surface on a pressure responsive member such as a diaphragm, which raised surface forms an obturator moveable with respect to a valve seat. The obturator is contacted by an operating member extending through an exhaust port valve seat in the valving chamber and the operating member is operatively moved by the solenoid armature. The pressure responsive member preferably in the form of an elastomeric diaphragm has the obturator preferably formed by a rigid insert in the central region of the diaphragm. A bleed orifice provides limited flow across the pressure responsive member to provide viscous dampening of the movement of the obturator. Viscous dampening of the movement of the pressure responsive member and obturator render the valve substantially insensitive to instability and flutter when the valve supply port is subject to transients the valve body is subjected to vibration or the valve is in the nearly closed condition.